90-91 suburban cluster swap issue
 

So I did the swap and thought it was all good. Then I go to start the truck and the speedo starts acting like a tach. Yes, a tach. I smash the accelerator and the speedo needle moves. This is happening with the vss wire coming from ecm to pin 18 on the cluster plug. What did I do wrong? Mind you that the white tach wire from ecm is not spliced in to anything.
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